The present invention pertains to sealed bearing assemblies, which are particularly useful in forming trolley wheels.
Trolley systems are employed extensively as overhead or in-floor motive arrangements in manufacturing processes. Typically, semi-precision bearings are utilized in this environment to rollingly support a trolley adapted to transport workpieces, tools, etc., for movement along a track. Semi-precision bearings are well suited to this task due to the inherent clearance or "play" or looseness incorporated in their construction. More specifically, the looseness of the bearing enhances its ability to maneuver curves, pass smoothly over debris that may be on the track, and accommodate element expansion in processes involving large temperature gradients.
Yet, despite the number of advantages gained, the construction thereof providing the desired looseness has also been responsible for several notable shortcomings. Firstly, loose bearings are difficult to seal due to the relatively large radial and axial excursions of the rotating components. Most seals have a comparatively limited ability to follow such excursions and continue sealing. Secondly, because of the loose construction and the difficulty of conventional seals to remain in sealing contact, the grease contained within semi-precision bearings does, on occasion, seep out, drip onto and spoil the goods being manufactured. Thirdly, semi-precision bearings include a relatively large amount of enclosed open space which is filled with the lubricating grease. In the past, the consumption of such large amounts of grease has been inconsequential due to the low cost of conventional greases. However, technologically advanced greases--offering increased lubrication capabilities, longer lifespans, increased usefulness in high temperatures, etc.--are very expensive and have, heretofore, been essentially limited economically to precision bearings.